The present invention relates to a process for the treatment of Czochralski single crystal silicon wafers to dissolve existing oxygen clusters and precipitates, while preventing their formation upon a subsequent oxygen precipitation heat treatment. The process comprises rapid thermal annealing the wafer to dissolve existing oxygen clusters and precipitates. The rapid thermal anneal is performed in an atmosphere capable of oxidizing the surface of the wafer thereby causing an inward flux of silicon self-interstitial atoms in order to reduce the number density of vacancies in the single crystal silicon to a value such that oxygen precipitates will not form if the wafer is subsequently subjected to an oxygen precipitation heat-treatment.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A process for heat-treating a Czochralski single crystal silicon wafer to dissolve pre-existing oxygen precipitates, the process comprising heat-treating the wafer in a rapid thermal annealer at a temperature of at least about 1150 C. in an atmosphere having an oxygen concentration of at least about 1000 ppma to control the crystal lattice vacancy concentration to produce a wafer in which the formation of oxygen precipitates in a subsequent oxygen precipitation heat treatment is prevented and wherein the rapid thermally annealed wafer comprises a region having a substantially uniform concentration of oxygen interstitial atoms which extends from the center of the wafer to a distance of no greater than 15 microns from the surface of the wafer.
2. The process of claim 1 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 10 microns from the surface of the wafer.
3. The process of claim 1 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 5 microns from the surface of the wafer.
4. The process of claim 1 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 3 microns from the surface of the wafer.
5. The process of any one of claims 1 - 4 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 50%.
6. The process of any one of claims 1 - 4 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 20%.
7. The process of any one of claims 1 - 4 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 10%.
8. A process for heat-treating a Czochralski single crystal silicon wafer to dissolve pre-existing oxygen precipitates, the process comprising heat-treating the wafer in a rapid thermal annealer at a temperature of at least about 1150 C. and controlling the rate of cooling from the maximum temperature achieved during the heat-treatment through a temperature range in which vacancies are relatively mobile for a time period sufficient to reduce the number density of crystal lattice vacancies in the cooled wafer prior to cooling the wafer below the temperature range in which vacancies are relatively mobile, to produce a wafer in which the number density of vacancies in the single crystal silicon has been reduced to a value such that oxygen precipitates will not form in the heat-treated wafer upon subjecting the wafer to an oxygen precipitation heat-treatment and wherein the thermally annealed wafer comprises a region having a substantially uniform concentration of oxygen interstitial atoms which extends from the center of the wafer to a distance of no greater than 15 microns from the surface of the wafer.
9. The process of claim 8 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 10 microns from the surface of the wafer.
10. The process of claim 8 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 5 microns from the surface of the wafer.
11. The process of claim 8 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 3 microns from the surface of the wafer.
12. The process of any one of claims 8 - 11 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 50%.
13. The process of any one of claims 8 - 11 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 20%.
14. The process of any one of claims 8 - 11 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 10%.
15. A process for heat-treating a Czochralski single crystal silicon wafer to dissolve pre-existing oxygen clusters and to prevent future precipitate formation resulting from an oxygen precipitation heat treatment, the process comprising: heat-treating the wafer at a temperature of at least about 1150 C. in a rapid thermal annealer to dissolve pre-existing oxygen clusters; cooling the heat-treated wafer to a temperature between about 950 and 1150 C. at a rate in excess of about 20 C.; thermally annealing the cooled wafer at a temperature between about 950 and 1150 C. for a time period sufficient to reduce the number density of crystal lattice vacancies in the cooled wafer prior to cooling the wafer below a temperature of about 950 EC, to produce a wafer in which the formation of oxygen precipitates in a subsequent oxygen precipitation heat treatment is prevented and wherein the rapid thermally annealed wafer comprises a region having a substantially uniform concentration of oxygen interstitial atoms which extends from the center of the wafer to a distance of no greater than 15 microns from the surface of the wafer.
16. The process of claim 15 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 10 microns from the surface of the wafer.
17. The process of claim 15 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 5 microns from the surface of the wafer.
18. The process of claim 15 wherein the region having a substantially uniform concentration of oxygen interstitial atoms extends from the center of the wafer to a distance of no greater than 3 microns from the surface of the wafer.
19. The process of any one of claims 15 - 18 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 50%.
20. The process of any one of claims 15 - 18 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 20%.
21. The process of any one of claims 15 - 18 wherein the concentration of oxygen interstitial atoms in the substantially uniform region has a variance of no more than about 10%.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 14, 2001
August 13, 2002
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